1. Field of the Invention
The present invention relate to a liquid crystal display device, and more particularly, to a method of manufacturing an array substrate for a liquid crystal display device.
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, however, many efforts and studies are being made to develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as substitutes for the CRTs. Of these flat panel displays, LCD devices have many advantages, such as high resolution, light weight, thin profile, compact size, and low voltage power supply requirements.
In general, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into the direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
The LCD device using an electric field induced in a vertical direction has disadvantage in viewing angles. To solve this problem, an in-plane switching (IPS) mode LCD device using an in-plane electric field is proposed.
FIG. 1 is a schematic cross-sectional view illustrating an IPS mode LCD device according to the related art.
Referring to FIG. 1, the IPS mode LCD device includes an array substrate 1, a color filter substrate 3 and a liquid crystal layer 5.
The array substrate 1 includes pixel and common electrodes 25 and 21 producing an in-plane electric field L. The liquid crystal layer 5 is operated by an electric field L. This configuration makes viewing angles wide.
The pixel and common electrodes have a width of about 2.2 μm or less to improve aperture ratio and have a double-layered structure using different conductive materials to reduce reflectance for ambient light and improve ambient contrast ratio. However, the double-layered structure causes some problems as follows.
Referring to FIG. 2, which is a picture illustrating a part of the second conductive material not etched but remaining as residues in a granular form according to the related art, the residues in a granular form remains not only over the pixel and common electrodes 25 and 21 but also over a large area other than the pixel and common electrodes 25 and 21. Accordingly, the granular residues affect an electric field to operate the liquid crystal layer 5 and reduce response speed of liquid crystal thus. Further, since the granular residues acts as haze ingredients, brightness is reduced.
Further, the granular residues cause defects in rubbing an alignment layer which is formed on the pixel and common electrodes 25 and 21.